Answer:
Although answer is incomplete, I would assume that you would add the three numbers up.
Explanation
Equation: 6.6 + 4.4 + 2.75 weeks
Step 1. Add either numbers. I decided to do this - 6.6 +4.4 = 11.0
Step 2. Add eleven to 2.75 - 11.0 + 2.75 = 13.75
Step 3. Finalize answer; 13.75 weeks
Check:
I will subtract the 3 numbers in the same order I added them in.
Step 1. 13.75 - 2.75 = 11.0
Step 2. 11.0 - 6.6 = 4.4
Check is valid so the answer is correct.
Hope this helps.